Ongoing Mysteries of Life

The question of why evolution has developed a certain feature, and why it sustains it, is far from completely answered. There are still a lot of mysteries that Mother Nature knows the answers to that I don’t. The following are some of the questions in my Unsolved Mysteries file. They have little to do with thinking, but they are fascinating nonetheless.

Blood, the Ageless Tissue

One day I asked my niece, who was well on her way to becoming a doctor, “Can you tell a person’s age from their blood?”

Her answer was quick and direct. “No, you can’t … except for a very young baby’s blood. The blood of a fetus has a different kind of hemoglobin because it’s getting oxygen from a placenta, not lungs.”

This was not the answer I was expecting, so I thought about it, and came up with interesting thoughts.

This means blood is an ageless tissue, which makes it very different from skin, muscle, eyes … almost every other tissue in the human body. All these other tissues are changing constantly with age.

So its performance of its tasks remains almost constant throughout life. It always carries the same amount of oxygen and carbon dioxide, nutrients and waste products, and its immune and clotting systems also remain near constant.

This constant nature explains why doctors love to take blood samples and run diagnostics on them. If healthy blood is nearly a constant, then deviations are easy to measure.

Still, it’s a mystery that blood doesn’t rise and decline in effectiveness the way other tissues do.

Why Is Five the Right Number for Fingers and Toes?

Mammals and modern reptiles tend to have five digits on their feet. I don’t know why. I’ve seen actual cats with six and seven toes, and pictures of people with four and six fingers, so it’s clear that Mother Nature could select other numbers if they were better choices. Birds, like the theropod dinosaurs they evolved from, have three claws, and hooved mammals are divided into even-toed (two or four) and odd-toed (one or three); so fewer digits are also possible.

Although in all these cases there are five buds started in the fetus, like human tails they don’t keep growing.

Five seems to be the right number for us and many of our relatives … but I haven’t yet figured out why.

Why Are Males Larger than Females?

Is the fact that human males generally grow larger than females a controllable benefit of the human form, or an uncontrollable “live with it” feature?

Female insects, birds, and reptiles are generally bigger than males. The strong justification for this is that it takes a lot more resource to produce eggs than it does to produce sperm, so a bigger body for egg-makers is helpful.

Is the converse in mammals a necessary evil that comes as part of the testosterone / estrogen hormone system, a tradeoff for valuable features, or is it a benefit in its own right?

In mankind, this phenomenon has made males cooperative bread-winners and protectors for females. But is this merely a lemons to lemonade transformation, or is the larger male a benefit for our fellow mammals in general?

Is Loss of Vitamin C Synthesis a Marker for a Beneficial Mutation?

Humans and other “dry-nosed” primates (the haplorhines) don’t successfully synthesize Vitamin C from its components because of a single mutation to the DNA coding for a single liver enzyme. The only other familiar mammal that can’t make Vitamin C is the guinea pig.

We can get plenty of already-assembled Vitamin C from plant and animal sources, so the mutation is neutral, neither beneficial or harmful. Another example of a neutral mutation is iris color—blue eyes and brown eyes work equally well.

In theory, because it makes no difference to reproductive success a neutral mutation of a single gene should drunk-walk in the gene pool, sometimes spread and sometimes shrink. Eye color does.

But no haplorhines synthesize Vitamin C, which means the change has acted like a very favorable mutation, not a neutral one. Therefore, I speculate that the Vitamin C mutation is a genetic marker for some other very favorable mutation that has spread widely through the haplorhine and guinea pig gene pool.